Anchoring Element for Use in Bone

ABSTRACT

An anchoring element for use in bone has a proximal end and a distal end. The distal end may be embedded in bone with the proximal end exposed. An abutment surface is disposed toward the proximal end. The anchoring element includes four surfaces that define the distal end. A generally cylindrical first surface defines an exterior of the anchoring element and includes a first external thread having a pitch. An annular second surface is disposed toward the distal end and joined to the first surface along an outer circumference of the second surface. A third surface concentric with the first surface is joined to the second surface along an inner circumference of the second surface. A fourth surface disposed between the distal end and the proximal end of the first surface is joined to the third surface along an outer circumference of the fourth surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/539,633 filed on Jan. 28, 2004.

BACKGROUND OF THE INVENTION

Anchoring elements are used in a variety of dental, medical, andsurgical procedures where it is desired to embed a mechanical attachmentinto living bone. One example of a procedure that uses anchoringelements is dental prosthesis using embedded implants.

Dental implants provide a desirable prosthesis for patients who aremissing one or more natural teeth. A dental implant includes ananchoring element that is embedded into the jawbone and a prosthetictooth that is attached to and supported by the anchoring element. Theprosthetic tooth may be attached directly to the anchoring element or anabutment fixture may be attached to the anchoring element and supportthe prosthetic tooth in turn. An appropriate anchoring element willsupport bone growth that invades the anchoring element such that theanchoring element becomes integrated with the surrounding bone in aprocess termed osseointegration.

An anchoring element to support a prosthetic tooth may be embedded inwhat is termed a two-stage procedure. In the first stage, the anchoringelement is embedded into the jawbone and the surgical site is thenclosed. After a period of months the anchoring element will achieveosseointegration. The site of the anchoring element is then re-openedsurgically to allow the attachment of a prosthetic tooth.

More recently techniques have been developed that permit a dentalimplant to be embedded in a one-stage procedure. In a one-stageprocedure, the anchoring element is embedded and a prosthetic tooth isimmediately fitted. The immediately fitted prosthetic tooth may be aninterim prosthesis that allows the soft tissue to properly heal andmaintains the spacing and alignment of adjacent teeth during the periodof osseointegration. A permanent prosthetic tooth may be fitted at alater date after at least some osseointegration has occurred withoutrequiring an additional surgical procedure.

To achieve successful osseointegration it is necessary that theanchoring element fit closely into the surrounding bone, generallyhaving a gap of no more than 1.5 millimeters. It is also important thatthe anchoring element not move relative to the surrounding bone duringthe period of osseointegration. Where the anchoring element cannot beclosely fitted to the surrounding bone, it may be necessary to usebone-grafting materials to fill the space between the anchoring elementand the surrounding bone.

Molars are commonly missing teeth. The use of an implant to replace amolar presents some special difficulties. Molars generally have multipleroots. The mandibular molars of the lower jaw generally have two roots.The maxillary molars of the upper jaw generally have three roots. In afresh extraction site the void left by the molar roots presents a sitethat can be difficult to fit with an anchoring element. In addition, thebone in the molar region of the jaw generally consists of a thin hardlayer of cortical bone surrounding a core of softer spongy cancellousbone. The cancellous bone may provide poor support for the anchoringelement prior to osseointegration.

A molar is a relatively large tooth and it is desirable to use ananchoring element having a relatively large diameter to fill the voidfollowing an extraction. However, the use of a wide anchoring elementmay require that a significant amount of bone be removed from theextraction site to accommodate the anchoring element. This may leaveonly a small amount of cortical bone available to support the anchoringelement which may be embedded in predominantly cancellous bone. Inparticular, the use of a wide anchoring element may require removal ofthe triangular mound-shaped mass of bone that is found between the rootsknown as the interradicular bone. Thus, it is difficult to place ananchoring element in a fresh molar extraction site with sufficientstability to allow embedding of a dental implant with a one-stageprocedure.

Another circumstance that can present difficulties in placing ananchoring element for a dental implant occurs in cases where it isdesired to place a dental prosthesis in a healed extraction site. When amolar is lost, the alveolar ridge that supports the teeth is fairlyrapidly resorbed. This causes a loss of height of the jawbone in thearea of tooth loss. When an anchoring element is to be embedded in ahealed extraction site, it may not be possible to place an anchoringelement to a very great depth.

In the lower jaw, the presence of the mandibular alveolar nerve in thelower jaw limits the depth of the anchoring element. In the upper jawthe maxillary sinus limits the depth. These limiting anatomical featuresmay require the use of a short anchoring element, perhaps 5 to 8millimeters in length. The use of short anchoring elements for suchcases has a lower rate of long-term success because of the reducedsurface area available for osseointegration.

It would be desirable to have an anchoring element that can be used toplace a dental implant in the molar area both for fresh extraction sitesand for healed sites.

SUMMARY OF THE INVENTION

An anchoring element for use in bone has a proximal end and a distalend. The distal end may be embedded in bone with the proximal endexposed. An abutment surface is disposed toward the proximal end. Theanchoring element includes four surfaces that define the distal end. Agenerally cylindrical first surface defines an exterior of the anchoringelement. At least a portion of the first surface includes a firstexternal thread having a pitch. An annular second surface is disposedtoward the distal end and the first surface is joined to the secondsurface along an outer circumference of the second surface. A thirdsurface concentric with the first surface is joined to the secondsurface along an inner circumference of the second surface. At least aportion of the third surface may include an internal thread having thepitch of the first external thread. A fourth surface disposed betweenthe distal end and the proximal end of the first surface is joined tothe third surface along an outer circumference of the fourth surface.

In another embodiment, an anchoring element includes six surfaces thatdefine the distal end. At least a portion of a first surface includes afirst external thread. An annular second surface is disposed toward thedistal end and joined to the first surface along an outer circumferenceof the second surface. A third surface concentric with the first surfaceis joined to the second surface along an inner circumference of thesecond surface. An annular fourth surface is disposed between the distalend and the proximal end and joined to the third surface along an outercircumference of the fourth surface. A fifth surface concentric with thefirst surface is joined to the fourth surface along an innercircumference of the fourth surface. A sixth surface is disposed towardthe distal end and joined to the fifth surface along an outercircumference of the sixth surface.

In another embodiment, an anchoring element for use in bone has aproximal end and a distal end. The distal end may be embedded in bonewith the proximal end exposed. The anchoring element includes agenerally cylindrical first surface, at least a portion of the firstsurface including an external thread. An abutment surface is disposed atthe proximal end of the anchoring element. The abutment surface is at anangle to an axis from the proximal end to the distal end of theanchoring element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view of an anchoring element for use in bone thatembodies the invention.

FIG. 2 is a plan view of the distal end of the anchoring element shownin FIG. 1.

FIG. 3 is a cross section of the anchoring element taken along the line3-3 shown in FIG. 2.

FIG. 4 is a plan view of the distal end of the anchoring element ofFIGS. 1 through 3.

FIG. 5 is a side elevation of another anchoring element that embodiesthe invention.

FIG. 6 is a plan view of the proximal end of the anchoring element ofFIG. 5.

FIG. 7 is a cross section taken along section line 7-7 shown in FIG. 6.

FIG. 8 is a plan view of the proximal end of the anchoring element ofFIGS. 5 through 7.

FIG. 9 is a pictorial view of another anchoring element that embodiesthe invention.

FIG. 10 is a plan view of the proximal end of the anchoring element ofFIG. 9.

FIG. 11 is a cross section of the anchoring element taken along the line11-11 shown in FIG. 10.

FIG. 12 is a plan view of the distal end of the anchoring element ofFIGS. 9 through 11.

FIG. 13 is a cross section of the anchoring element with the distalportion taken along the section line 13-13 shown in FIG. 12 and theproximal portion taken along the section line 11-11 shown in FIG. 10.

FIG. 14 is a cross section view of another anchoring element thatembodies the invention.

FIG. 15 is a cross section of the anchoring element shown in FIG. 14with the distal portion sectioned similarly to the view of FIG. 13.

FIG. 16 is a cross section of a mandibular molar extraction site.

FIG. 17 is a cross section of the extraction site shown in FIG. 16.

FIG. 18 is a cross section similar to the view of FIG. 16 showing thepreparation of the extraction site for embedding an anchoring element.

FIG. 19 is a cross section of the upper portion of the extraction siteshown in FIG. 18.

FIG. 20 is a cross section of the lower portion of the extraction siteshown in FIG. 18.

FIG. 21 is a cross section of an anchoring element embedded in theextraction site prepared as shown in FIG. 18.

FIG. 22 is a cross section of a first part of another anchoring elementthat embodies the invention.

FIG. 23 is a side view of a second part of the anchoring element.

FIG. 24 is a view of the second part shown in side view installed intothe first part shown in cross section to form the anchoring element.

FIG. 25 is a view of an alternate position for the second part relativeto the first part of the anchoring element shown in FIG. 24.

FIG. 26 is a cross section of a first part and side view of a secondpart forming another anchoring element that embodies the invention.

FIG. 27 is a cross section of a first part and side view of a secondpart forming another anchoring element that embodies the invention.

FIG. 28 is a cross section of a first part of another anchoring elementthat embodies the invention.

FIG. 29 is a side view of a second part of the anchoring element.

FIG. 30 is a view of the second part shown in side view installed intothe first part shown in cross section to make the complete anchoringelement.

FIG. 31 is a cross section of another anchoring element that embodiesthe invention.

FIG. 32 is a cross section of another anchoring element that embodiesthe invention.

FIG. 33 is a cross section of another anchoring element that embodiesthe invention shown as it may be embedded in bone.

FIG. 34 is a side view of another anchoring element that embodies theinvention.

FIG. 35 is a side view of another anchoring element that embodies theinvention.

FIG. 36 is a cross section of another anchoring element that embodiesthe invention.

FIG. 37 is a cross section of another anchoring element that embodiesthe invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an anchoring element 100 for use in bone that embodies theinvention. The anchoring element may be fabricated of any biocompatiblematerial known or discovered to promote osseointegration such astitanium or a titanium alloy. The portions of that are to be in intimatecontact with bone can display various surface characteristics. Theseportions can be titanium plasma sprayed, coated with hydroxy-apatite (HAcoated), surface machined, sand blasted, or acid etched to promoteosseointegration.

For convenience in description, the anchoring element 100 will bedescribed with reference to a distal end and a proximal end. The distalend is shown in FIG. 1 as the end to the lower right and is the end thatis embedded to the greatest depth in bone. The proximal end is the endto the upper right and is the end that may be exposed when the anchoringelement 100 is embedded in bone.

The anchoring element 100 includes a first surface that is a generallycylindrical exterior surface of the anchoring element. The term“generally cylindrical” is used to describe a surface that issubstantially rotationally symmetric about an axis that extends from thedistal end to the proximal end. The first surface may include a screwthread 112. It will be appreciated that a screw thread is notrotationally symmetric in the strictest sense. A screw thread or similarfeature is intended to be included by the term “substantiallyrotationally symmetric.” The exterior surface of the anchoring element100 may include features such as the aforementioned screw thread andother features such as shoulders 102, tapered portions 110, and thelike, all of which are intended to be included by the term “generallycylindrical.”

At least a portion of the first surface of the anchoring element 100 mayinclude a first external thread 112 having a pitch. The thread 112 maybe of any of a variety of forms known or discovered to be effective forembedding the anchoring element in bone. The thread 112 may includeself-threading (thread cutting) features or other features that aid inembedding the anchoring element into bone or that promoteosseointegration.

The first surface may include a frustrated first conical portion 110adjacent the distal end of the anchoring element 100 such that a smallercircumference of the first conical portion is adjacent the distal end.The first conical portion 110 may facilitate placing the anchoringelement 100 into a hole that is prepared in the bone to receive theanchoring element. The first conical portion 110 may provide a somewhatsmaller leading distal end that allows the anchoring element 100 toinitially engage the bone with minimal force and align the anchoringelement to the hole that has been prepared in the bone.

The first conical portion 110 may be unthreaded or may partially orfully intersect the first external thread 112. In one embodiment thefirst conical portion 110 may have a smallest diameter at the distal endof the anchoring element 100 that is approximately a root diameter ofthe first external thread. The first conical portion 110 may graduallyincrease in diameter toward the proximal end thereby providing agradually increasing thread depth.

The anchoring element 100 may include an abutment surface disposedtoward the proximal end of the first surface. The abutment surface maybe of any of a variety of known or discovered forms that permitattachment to the anchoring element.

FIGS. 1 through 3 illustrate an abutment surface that may be provided toreceive a dental prosthesis. The illustrated abutment surface includesan external hex surface 104 that may provide a wrenching surface forembedding the anchoring element 100. The illustrated abutment surfacefurther includes a locating recess 106 and an internal anchoring thread108 to receive a devices that is coupled to the anchoring element by ascrew.

The anchoring element 100 includes an annular second surface 120disposed toward the distal end of the first surface and joined to thefirst surface along an outer circumference 122 of the second surface.The second surface 120 may engage the bottom of the hole that has beenprepared in the bone and thereby contribute significantly to thestability of the embedded anchoring element 100. The second surface 120may be substantially flat or may have a rounded or other shape chosen toeffectively cooperate with the bottom of the hole that has been preparedin the bone to provide initial stability.

As may be seen in the plan view of the distal end, the anchoring element100 includes a third surface 140 concentric with the first surface andjoined to the second surface 120 along an inner circumference 124 of thesecond surface. At least a portion of the third surface 140 may includean internal thread having the pitch of the first external thread suchthat both threads will advance the anchoring element 100 at the samerate as it is rotated to embed the anchoring element into bone. Theinternal thread may be of any of a variety of forms known or discoveredto be effective for embedding the anchoring element in bone. Theinternal thread may include self-threading (thread cutting) features orother features that aid in embedding the anchoring element into bone orthat promote osseointegration. It is contemplated that the hole in thebone that is prepared to receive the anchoring element 100 may leaveresidual bone in place such that the third surface 140 will at leastpartially engage the bone to provide additional initial stability and anadditional surface for osseointegration.

The third surface 140 may include a frustrated second conical portionadjacent the distal end such that a larger circumference of the secondconical portion is adjacent the distal end. The second conical portionmay facilitate placing the anchoring element 100 into the portion ofhole that includes residual bone. The second conical portion maycompress the residual bone as the anchoring element 100 is embedded tofurther increase initial stability.

The second conical portion may be unthreaded or may partially or fullyintersect the first internal thread. In one embodiment the secondconical portion may have a largest diameter at the distal end of theanchoring element 100 that is approximately a root diameter of the firstinternal thread. The second conical portion may gradually increase indiameter toward the proximal end thereby providing a graduallyincreasing thread depth.

The anchoring element 100 includes a fourth surface 130 disposed betweenthe distal end and the proximal end and joined to the third surface 140along an outer circumference of the fourth surface 132. It iscontemplated that the hole in the bone that is prepared to receive theanchoring element 100 may leave an upper surface on the residual bonesuch that the fourth surface 130 will engage the upper surface toprovide additional initial stability and an additional surface forosseointegration.

FIG. 3 is a cross-section of the anchoring element 100 taken along adiameter as shown by the section line 3--3 in FIG. 2. FIG. 3 may aid invisualizing the relationships between the various surfaces of theanchoring element 100. FIG. 3 may also aid in visualizing a possibleinteraction of the conical sections with the threads at the distal end.

FIGS. 5 through 8 illustrate another anchoring element 200 that embodiesthe invention. This embodiment includes many features that are similarto the anchoring element 100 illustrated by FIGS. 1 through 4. Similarfeatures for anchoring element 200 have been given reference numeralsthat are the reference numerals used for anchoring element 100 increasedby 100.

In this embodiment the anchoring element 200 includes an abutmentsurface 204 in the form of a frustrated square pyramid. The abutmentsurface 204 may provide a wrenching surface. If the anchoring element isused to support a dental prosthesis, a prosthetic tooth may be directlycoupled to the abutment surface 204 such as by cement.

FIG. 7 shows a cross section of the anchoring element 200 taken alongthe section line 7--7 as shown in the plan view of the proximal end ofFIG. 6. The first surface may be a slightly larger in diameter than thethird surface. It may be seen in FIG. 7 that there will be acomparatively thin cross-section where the roots of the external thread212 coincide with the internal thread. It may be advantageous to arrangethe internal threads so that the roots coincide with the crest of theexternal thread to avoid a thin cross section.

The anchoring element 200 may be relatively short such that if the firstand/or third generally cylindrical surfaces include a conical section,the conical section may occupy all or substantially all of the firstand/or third surfaces.

FIGS. 9 through 13 illustrate another anchoring element 300 thatembodies the invention. This embodiment includes many features that aresimilar to the anchoring element 100 illustrated by FIGS. 1 through 4.Similar features for anchoring element 300 have been given referencenumerals that are the reference numerals used for anchoring element 100increased by 200.

FIGS. 10 and 11 illustrate an abutment surface that may be provided toreceive a dental prosthesis. The illustrated abutment surface includes alobed locating recess 306 and an internal anchoring thread 308 toreceive a devices that is coupled to the anchoring element 300 by ascrew. The lobes of the locating recess 306 may prevent rotation of acoupled device and may provide a wrenching surface for embedding theanchoring element 300.

In this embodiment the anchoring element the fourth surface 330 isannular. The anchoring element further includes a fifth surface 350concentric with the first surface and joined to the fourth surface 330along an inner circumference 334 of the fourth surface. A sixth surface360 is disposed toward the distal end of the first surface and joined tothe fifth surface 350 along an outer circumference 362 of the sixthsurface.

The fifth surface 350 may include a second external thread on all orpart of the fifth surface. The second external thread has the pitch ofthe first external thread such that all threads will advance theanchoring element 300 at the same rate as it is rotated to embed theanchoring element into bone. The second external thread may be of any ofa variety of forms known or discovered to be effective for embedding theanchoring element in bone. The second external thread may includeself-threading (thread cutting) features or other features that aid inembedding the anchoring element into bone or that promoteosseointegration. It is contemplated that the hole in the bone that isprepared to receive the anchoring element 300 may provide a secondaryhole in the residual bone such that the fifth surface 350 will at leastpartially engage the bone to provide additional initial stability and anadditional surface for osseointegration.

The fifth surface 350 may include a frustrated third conical portionadjacent the distal end such that a smaller circumference of the thirdconical portion is adjacent the distal end. The third conical portionmay be unthreaded or may partially or fully intersect the secondexternal thread on the fifth surface 350. In one embodiment the thirdconical portion may have a smallest diameter at the distal end of theanchoring element 300 that is approximately a root diameter of thesecond external thread. The third conical portion may gradually increasein diameter toward the proximal end thereby providing a graduallyincreasing thread depth. The second and third conical sections may actto compress the residual bone between the third and fifth generallycylindrical surfaces.

FIG. 13 is a cross-section view of anchoring element 300 shown in FIGS.9-12 where the lower part of the cross-section is taken along sectionline 13--13 shown in FIG. 12 so that the fifth surface is not cut by thecross-section and the fifth surface may be seen. The portion of thecross-section between the fourth surface 330 and the proximal end istaken along section line 11--l1 shown in FIG. 10.

FIGS. 14 and 15 illustrate another anchoring element 400 that embodiesthe invention. This embodiment includes many features that are similarto the anchoring element 300 illustrated by FIGS. 9 through 13. Similarfeatures for anchoring element 400 have been given reference numeralsthat are the reference numerals used for anchoring element 300 increasedby 100.

In this embodiment the anchoring element 400 the first surface includesa shoulder surface 402 in the form of a frustrated conical section. Sucha conical shoulder is intended to be included by the term “generallycylindrical.” The anchoring element 400 may be relatively short suchthat an internal anchoring thread 408 extends into the portion of theanchoring element 400 defined by the fifth surface 450.

FIGS. 16 through 20 illustrate an exemplary use of an anchoring element500 that embodies the invention to provide a dental prosthesis for anextracted molar tooth.

FIG. 16 shows a cross-section of a socket following the extraction of amandibular molar having two roots. The cross-section is taken along asection line that is mesiodistal (running from the front to the back ofthe head). The socket includes the interradicular bone 510 whichseparated the roots of the extracted molar.

FIG. 17 shows a cross-section of the socket viewed from the top andlooking down into the socket. An outline of the cervical collar 512taken along section line 17A--17A in FIG. 16 is shown. An outline ofeach of the two roots 514, 516 taken along section line 17B--17B in FIG.16 is shown.

FIG. 18 shows a cross-section of a prepared molar socket which is thesocket of FIG. 16 after a hole has been prepared to receive theanchoring element. FIG. 19 is a top down cross-section of the preparedmolar socket at the cervical collar 512 taken along section line 19--19in FIG. 18. It may be seen the prepared hole 520 may not remove all ofthe cervical collar 512. Generally it is desirable to provide a largeperiphery of contact between the anchoring element 500 and the cervicalcollar 512 to provide good initial stability. However, it is alsodesirable to preserve as much bone as possible consistent with preparinga hole that will provide good initial stability and goodosseointegration. In particular, the bone may have a relatively thin andhard cortical layer surrounding a softer inner core of cancellous bone.It is desirable preserve the cortical bone which will provide much moreinitial stability than the spongy cancellous bone.

The anchoring element 500 may be sized to come within at least 1.5millimeters of all parts of the socket so that osseointegration willoccur. The anchoring element 500 may be sized so that about 75% or moreof the periphery at the cervical collar is in direct contact with theanchoring element to provide good initial stability.

FIG. 20 shows a cross-section of the socket of FIG. 16 after a hole hasbeen prepared to receive the anchoring element. FIG. 20 is a top downcross-section of the prepared hole at the roots 514, 516 taken alongsection line 20--20 in FIG. 18. It may be seen the prepared hole 522 maynot remove all of the socket that surrounded the roots. It may also beseen that a substantial portion of the interradicular bone 510 ispreserved as residual bone in the prepared molar socket. The distalportion of the prepared hole 522 includes an annular region 524 toreceive the portion of the anchoring implant between the first surface501 and third surface 503. The second surface 502 of the anchoringelement 500 may bear against the bottom surface 524 of the molar socket522 to increase initial stability of the anchoring element.

The bottom surfaces 530, 532, 534 of the prepared hole are alsosignificant. It is desirable that the bottom surfaces support asignificant portion of one or more of the second surface 502, fourthsurface 504, and sixth surface 506 (if present) of the anchoring element500. For this reason, the hole may be prepared with bottom surfaces 530,534 that are below the lowest point of the roots if permitted by otheranatomical structures such as the mandibular nerve 518 or maxillarysinus. A flat surface 532 may be prepared on the proximal portion of theresidual interradicular bone 510 to support the fourth surface 504. Theflat surface 532 on the proximal portion of the residual interradicularbone 510 may be generally parallel to the bottom surface 530 of theprepared molar socket 500.

The first surface 501 of the anchoring element 500 is adapted tothreadedly engage the outer wall 522 of the molar socket. The firstsurface 501 may include a frustrated first conical portion adjacent thesecond surface 502 such that a smaller circumference of the firstconical portion is adjacent the second surface. The conical surface mayaid in placing the anchoring element into the prepared molar socket. Theconical surface may compress the bone surrounding the outer wall of theprepared molar socket, particularly in the upper portion adjacent thecervical collar, which may increase bone density and support for theanchoring element.

The third surface 503 of the anchoring element 500 is adapted to bearagainst a first surface 511 of the interradicular bone 510 thatgenerally faces the outer wall 522 of the molar socket. The thirdsurface 503 may have a frustrated conical form such that it may compressthe interradicular bone, particularly in the upper portion, which mayincrease bone density and support for the anchoring element 500. Thethird surface 503 may include screw threads, which may be self-cuttingthreads, for threadedly engaging the first surface 511 of theinterradicular bone 510.

The anchoring element 500 may include a fifth surface 505. The preparedmolar socket may therefore include a secondary hole 526 in the residualinterradicular bone 510 to receive the fifth surface 505. The fifthsurface may bear against a side wall of the secondary hole. The fifthsurface 505 may have a frustrated conical form such that it may compressthe interradicular bone, particularly in the upper portion, which mayincrease bone density and support for the anchoring element 500. Thefifth surface 505 may include screw threads, which may be self-cuttingthreads, for threadedly engaging the side wall of the secondary hole526.

FIGS. 22 through 25 show another anchoring element 600 that embodies theinvention. A first part 610 includes a first surface 601, a secondsurface 602, a third surface 603, and a fourth surface 604. A secondpart 620 includes a fifth surface 605 and a sixth surface 606. The fifthsurface 605 is joined to the fourth surface 604 by screwing the secondpart 620 into the first part 610. The resulting assembly provides ananchoring element 600 that has similar features to the anchoring element300 shown in FIG. 9. It may be possible to adjust the position of thesixth surface 606 relative to the second surface 602 as shown by FIGS.24 and 25.

FIG. 26 shows another anchoring element 700 that embodies the invention.A second part 720 is screwed into a first part 710 to provide ananchoring element 700 that has similar features to the anchoring element400 shown in FIG. 14. The second part 720 may be shaped so that it canscrewed into an interference fit with the first part 710 such that theanchoring element 700 functions as a single piece after assembly.

FIG. 27 shows another anchoring element 800 that embodies the invention.A second part 820 passes through an unthreaded opening 814 in a firstpart 810 to provide an anchoring element 800 that has similar featuresto the anchoring element 400 shown in FIG. 14. The second part 820 mayinclude a head surface 822 that bears against a shoulder surface 812 onthe first part when both parts are embedded in bone. When both parts areassembled into an anchoring element 800 by being embedded in bone, thesecond part 820 may be adjusted to change the distally directed pressureof the first part 810 against the bone.

FIGS. 28 through 30 show another anchoring element 900 that embodies theinvention. A first part 910 includes a first surface 901, a secondsurface 902, and a third surface 903. The third surface 903 extends fromthe distal end to the proximal end providing a through passage thatincludes an internal thread for a least a portion of the third surface.A second part 920 includes a fourth surface 904, a fifth surface 905,and a sixth surface 906. The second part 920 further includes a joiningsurface 922 that is generally cylindrical and concentric with the fifthsurface 905. At least a portion of the joining surface may include anexternal thread that mates with at least a potion of the threaded thirdsurface 903 of the first part 910. The third surface 903 is joined tothe fourth surface 904 by screwing the second part 920 into the firstpart 910. The resulting assembly provides an anchoring element 900 thathas similar features to the anchoring element 300 shown in FIG. 9.

FIG. 31 shows another anchoring element 1000 that embodies theinvention. This embodiment includes a first surface 1001, a secondsurface 1002, a third surface 1003, a fourth surface 1004, a fifthsurface 1005, and a sixth surface 1006 similarly arranged to previouslydescribed embodiments. In this embodiment the second surface 1002,fourth surface 1004, and sixth surface 1006 may be curved. In thisembodiment, only the first surface 1001 may include a threaded portion.The fifth surface 1005 may be a right cylinder such that this portion ofthe anchoring element 1000 may fit into a pilot hole that may have beenused to guide the preparation of the bone to receive the anchoringelement. The second surface 1002 may include a conical portion toprovide a close fit to residual bone.

FIG. 32 shows another anchoring element 1100 that embodies theinvention. This embodiment includes a first surface 1101, a secondsurface 1102, a third surface 1103, a fourth surface 1104, a fifthsurface 1105, and a sixth surface 1106 similarly arranged to previouslydescribed embodiments. The anchoring element 1100 of this embodiment isgenerally similar to the anchoring element 1000 of FIG. 31. The fifthsurface 1105 and the second surface 1102 may include conical portions toprovide a close fit to residual bone.

FIG. 33 shows another anchoring element 1200 that embodies theinvention. FIG. 33 is a cross-section of the anchoring element 1200embedded in the posterior portion of a mandible along section line in abucco-lingual (cheek to tongue) direction. This embodiment includes anabutment surface 1210 that is at an angle to an axis from the proximalend to the distal end of the first surface. The abutment surface 1210may be substantially flat in the area adjacent the proximal end of thefirst surface 1201. As shown in FIG. 33, when an anchoring element isembedded in a healed molar extraction site, resorption of the bone maycause the site to be shallow with a surface that may be higher on oneside 1220 than the other 1222, generally being lower to the buccal(cheek) side 1222. It may be seen that the angled abutment surface 1210allows the first surface 1201 to have greater contact with the bonewithout leaving a portion of the anchoring element 1201 exposed abovethe bone.

FIG. 34 shows another anchoring element 1300 that includes an abutmentsurface 1310 that is at an angle to an axis from the proximal end to thedistal end of the first surface.

FIG. 35 shows another anchoring element 1400 that includes an abutmentsurface 1410 that is at an angle to an axis from the proximal end to thedistal end of the first surface. In this embodiment the threaded portionof the first surface may extend to the abutment surface which mayincrease the threaded engagement of the anchoring element 1400 to bone.

FIG. 36 shows another anchoring element 1500 that embodies theinvention. This embodiment includes many features that are similar tothe anchoring element 200 illustrated by FIGS. 5 through 8. Similarfeatures for anchoring element 1500 have been given reference numeralsthat are the reference numerals used for anchoring element 200 increasedby 1300. The anchoring element 1500 includes a fourth surface 1530disposed between the distal end and the proximal end and joined to thethird surface 1540. The fourth surface 1530 is in the form of afrustrated cone. It is contemplated that the hole in the bone that isprepared to receive the anchoring element 1500 may leave an uppersurface on the residual interradicular bone such that the fourth surface1530 will engage the upper surface to provide additional initialstability and an additional surface for osseointegration. The conicalshape of the fourth surface may allow the residual interradicular boneto be selectively compressed as determined by how far into the molarsocket the anchoring element 1500 is advanced. This may allow a greaterdegree of compression to be applied when the residual interradicularbone is soft and spongy.

FIG. 37 shows another anchoring element 1600 that embodies theinvention. This embodiment includes many features that are similar tothe anchoring element 200 illustrated by FIGS. 5 through 8. Similarfeatures for anchoring element 1600 have been given reference numeralsthat are the reference numerals used for anchoring element 200 increasedby 1400. The anchoring element 1600 includes a fourth surface 1630disposed between the distal end and the proximal end and joined to thethird surface 1640. The fourth surface 1630 is in the form of a convexcurved surface. It is contemplated that the hole in the bone that isprepared to receive the anchoring element 1600 may leave an uppersurface on the residual interradicular bone such that the fourth surface1630 will engage the upper surface to provide additional initialstability and an additional surface for osseointegration. The convexshape of the fourth surface may allow the residual interradicular boneto be selectively compressed as determined by how far into the molarsocket the anchoring element 1600 is advanced. This may allow a greaterdegree of compression to be applied when the residual interradicularbone is soft and spongy.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention not be limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art. It is to be understoodthat individual features shown or described for one embodiment may becombined with individual features shown or described for anotherembodiment. It is to be understood some features are shown or describedto illustrate the use of the invention in the context of functionalanchoring elements and such features may be omitted within the scope ofthe invention.

1. An anchoring element for use in bone, the anchoring elementcomprising: a first surface having a distal end and a proximal end, atleast a portion of the first surface including a first external threadhaving a pitch; an abutment surface disposed toward the proximal end ofthe first surface; an annular second surface disposed toward the distalend of the first surface and joined to the first surface along an outercircumference of the second surface; a third surface concentric with thefirst surface and joined to the second surface along an innercircumference of the second surface; and a fourth surface disposedbetween the distal end and the proximal end of the first surface andjoined to the third surface along an outer circumference of the fourthsurface.
 2. The anchoring element of claim 1 wherein the first surfaceincludes a frustrated first conical portion adjacent the distal end suchthat a smaller circumference of the first conical portion is adjacentthe distal end.
 3. The anchoring element of claim 1 wherein the thirdsurface includes a frustrated second conical portion adjacent the distalend such that a larger circumference of the second conical portion isadjacent the distal end.
 4. The anchoring element of claim 1 wherein atleast a portion of the third surface includes an internal thread havingthe pitch of the first external thread.
 5. The anchoring element ofclaim 4 wherein the internal thread is self-threading.
 6. The anchoringelement of claim 1 wherein the fourth surface is annular, the anchoringelement further comprising: a fifth surface concentric with the firstsurface and joined to the fourth surface along an inner circumference ofthe fourth surface; and a sixth surface disposed toward the distal endof the first surface and joined to the fifth surface along an outercircumference of the sixth surface.
 7. The anchoring element of claim 6wherein the fifth surface includes a frustrated third conical portionadjacent the distal end such that a smaller circumference of the thirdconical portion is adjacent the distal end.
 8. The anchoring element ofclaim 6 wherein the first surface, the second surface, the thirdsurface, and the fourth surface are on a first part, the fifth surfaceand the sixth surface are on a second part, and the fifth surface isplaced adjacent to the fourth surface by passing the second part throughthe first part.
 9. The anchoring element of claim 6 wherein the firstsurface, the second surface, and the third surface are on a first part,the fourth surface, the fifth surface, and the sixth surface are on asecond part, and the fourth surface is placed adjacent to the thirdsurface by passing the second part through the first part.
 10. Theanchoring element of claim 6 wherein at least a portion of the thirdsurface includes a first internal thread having the pitch of the firstexternal thread and at least a portion of the fifth surface includes asecond external thread having the pitch of the first external thread.11. The anchoring element of claim 1 wherein the abutment surface is atan angle to an axis from the proximal end to the distal end of the firstsurface.
 12. An anchoring element suitable for placement in a preparedmolar socket that includes interradicular bone, the anchoring elementcomprising: abutment means for receiving a dental prosthesis; firstmeans for threadedly engaging an outer wall of the molar socket; secondmeans for bearing against a bottom surface of the molar socket; andthird means for bearing against a first surface of the interradicularbone that generally faces the outer wall of the molar socket.
 13. Theanchoring element of claim 12 wherein the first means includes afrustrated first conical portion adjacent the second means such that asmaller circumference of the first conical portion is adjacent thesecond means.
 14. The anchoring element of claim 12 wherein the thirdmeans is further for compressing the interradicular bone.
 15. Theanchoring element of claim 12 wherein the third means is further forthreadedly engaging the first surface of the interradicular bone. 16.The anchoring element of claim 15 wherein the third means is further forcutting a thread in the first surface of the interradicular bone. 17.The anchoring element of claim 12 further comprising: fifth means forbearing against a side wall of a hole prepared in the interradicularbone.
 18. The anchoring element of claim 17 wherein the fifth means isfurther for compressing the interradicular bone.
 19. The anchoringelement of claim 17 wherein the fifth means is further for threadedlyengaging the side wall of the hole in the interradicular bone.
 20. Amethod for placing an anchoring element to receive a dental prosthesisin a molar socket that includes interradicular bone, the methodcomprising: cutting a generally cylindrical outer wall in the molarsocket to receive a first surface of the anchoring element, the firstsurface having a distal end and a proximal end, at least a portion ofthe first surface including a first external thread having a pitch;cutting a generally annular flat surface in the molar socket at a distalend of the cylindrical outer wall to receive an annular second surfaceof the anchoring element, the second surface being disposed toward thedistal end of the first surface and joined to the first surface along anouter circumference of the second surface; cutting a generallycylindrical surface on the interradicular bone that generally faces theouter wall of the molar socket to receive a third surface of theanchoring element, the third surface being concentric with the firstsurface and joined to the second surface along an inner circumference ofthe second surface; placing the anchoring element into the molar socketby screwing the first surface into the outer wall of the molar socketuntil the second surface of the anchoring element bears against theannular flat surface in the molar socket and the third surface of theanchoring element bears against the cylindrical surface on theinterradicular bone.